USB_Init() no longer calls sei() to enable global interrupts - this must now be done in the user application once all init code has run.

Projects/LEDNotifier/LEDNotifier.c

@@ -107,6 +107,8 @@ int main(void)
 	
 	/* Create a regular blocking character stream for the interface so that it can be used with the stdio.h functions */
 	CDC_Device_CreateBlockingStream(&VirtualSerial_CDC_Interface, &USBSerialStream);
+	
+	sei();
 
 	for (;;)
 	{

Projects/LEDNotifier/LEDNotifier.h

@@ -40,6 +40,7 @@
 		#include <avr/io.h>
 		#include <avr/wdt.h>
 		#include <avr/power.h>
+		#include <avr/interrupt.h>
 		#include <string.h>
 		#include <stdio.h>